Membrane-Associated Respiratory Syncytial Virus F Protein Expressed from a Human Rhinovirus Type 14 Vector Is Immunogenic

Abstract

Human rhinovirus (HRV) replicons have the potential to serve as respiratory vaccine vectors for mucosal immunization in humans. However, since many vaccine immunogens of interest are glycosylated, an important concern is whether HRV replicons are capable of expressing glycosylated proteins. The human respiratory syncytial virus (RSV) fusion (F) protein was chosen as a model glycoprotein and the HRV replicon ΔP1FVP3 was generated by inserting the F protein-coding sequence in frame and in lieu of the 5′ proximal 1489 nucleotides of the capsid-coding segment in the HRV-14 genome. When transfected into H1-HeLa cells, ΔP1FVP3 replicated and led to the expression of the F protein. Inhibition with guanidine demonstrated that F-protein expression was dependent on ΔP1FVP3 replication and did not result from translation of input RNA. Although most of the F protein remained as an immature, glycosylated precursor (F0), a readily detectable fraction of the protein was processed into the mature glycosylated subunit F1, an event known to occur within the Golgi apparatus. Packaged ΔP1FVP3 replicons were generated in transfected HeLa cells by coexpression of homologous HRV capsid proteins using the vaccinia virus/T7 RNA polymerase hybrid system. Packaged replicon RNAs were capable of infecting fresh cells, leading to accumulation of the F protein as in RNA-transfected cells. Mice immunized with HeLa cell lysates containing F protein expressed from ΔP1FVP3 produced neutralizing antibodies against RSV. These results indicate that an HRV-14 replicon can express a foreign glycosylated protein, providing further support for the potential of HRV replicons as a vaccine delivery system.